1. Field of the Invention
The present invention relates to a novel and improved valve assembly for bulk containers with liner.
2. Description of Related Prior Art
Products made of thermoplastic materials can be manufactured by a number of different manufacturing procedures. The most commonly used methods are however, injection moulding, vacuum forming, blow moulding and press moulding.
Valves of butterfly and of ball type have been known for some time and they can be manufactured from thermoplastic material. Here injection moulding and press moulding are the most suited manufacturing methods in order to achieve the desired precision. Butterfly valves and ball valves made of thermoplastic materials are mostly used in low-pressure systems. Butterfly valves are often used in ventilation appliances were absolute closing isn't necessary. It is also possible to use the valves for fluid media. It will of course be important to have gaskets both in the valve seat as well as at the end of the valve housing. These gaskets are typically made from an elastomeric material, most commonly a thermoplastic material with a plasticizer additive. In many cases the valve is designed in such a way that material recovery is virtually impossible.
One area where such valves are frequently used is bulk goods where foldable pallet containers are provided with a bag shaped liner having a valve at the base intended for releasing the goods. This type of packaging is often used in the food industry and will therefore need attention regarding choice of material as well as hygiene. Steam sterilization of the valve area is frequently used before a container is connected to further processing and emptied. This will put some demands on the material used for making the components of the valve.
It is furthermore desirable to be able to recover packaging material after use which has proven difficult with previous solutions.